Dry natural gas premixing combustion is used for low-pollutant natural gas combustion. Premixing burners typically comprise a premixing zone in which air and fuel are mixed before the mixture is directed into a combustion chamber. The mixture burns in said chamber, with a hot gas being generated at increased pressure. The hot gas is transferred to the turbine. Premixing is of particular advantage in respect of nitrous oxide emissions since an even flame temperature obtains as a result of the homogeneous mixture. Nitrous oxide formation increases exponentially with the flame temperature. The primary consideration when operating premixing burners is thus to keep nitrous oxide emissions low and to avoid uncontrolled combustion, e.g. a flame blowback.
Syngas burners are characterized by the use of syngases as fuel in them. Compared to the classical turbine fuels of natural gas and oil, which essentially consist of hydrocarbons, the combustible elements of the syngases are essentially carbon monoxide and hydrogen. Depending on the gasification method and the overall plant concept, the heating value of the synthetic gas is around 5 to 10 times smaller than that of natural gas.
As well as the stoichiometric combustion temperature of the syngas the mixture quality between syngas and air at the flame front is a significant influencing variable for avoiding temperature peaks and thereby for minimizing thermal nitrous oxide formation.
The main elements of the syngases, in addition to carbon monoxide and hydrogen, are also inert components. The inert components involved are nitrogen and/or water vapor and where necessary also carbon dioxide. As a consequence of the low heating value, high volume flows of combustion gas must accordingly be introduced into the combustion chamber.
Current syngas combustion chambers are embodied as diffusion combustion chambers because of their high reactivity. Steam or nitrogen is usually used as a thinning agent in order to reduce thermal NOx formation. The use of steam/nitrogen as a thinning means in syngas combustion reduces the maximum level of efficiency of the overall system.                All previous syngas burners require the addition or mixing-in of an inerting medium (steam) to reduce the peak temperatures and thereby the NOx emissions. Because of the underlying design of the syngas burner with syngas as primary fuel however very large quantities of inerting medium would be necessary, making operating with natural gas economically unattractive, e.g. if the concept of diffusion combustion with addition of an inerting medium is also used in natural gas operation.        